For thousands of years, frequent fires, huge herds of grazing bison, scorching summer heat, and bitter cold winter winds shaped the tallgrass prairie, where grasses and colorful wildflowers adapted to a harsh environment that once blanketed the landscape above rich, fertile soils. In the 1800s, much of this prairie was converted to cropland and other uses, and less than 2% remains today. The Flint Hills region in Kansas, about 30 miles west of the Refuge, is the largest contiguous block of tallgrass prairie remaining in North America. Historically, Flint Hills National Wildlife Refuge was a mosaic of wet, moist, and dry tallgrass prairie habitats, but only a few fragments of true native tallgrass prairie remain there. The Refuge contains three types of tallgrass prairie habitats: cordgrass prairie in low, wet areas of the floodplain, composed mainly of prairie cordgrass, buttonbush, eastern gamagrass, and common ironweed; upland prairie on drier sites just above the floodplain, with big bluestem, Indiangrass, switchgrass, and many wildflowers such as lead plant, prairie blazing star, and purple prairie clover; and savanna, where scattered fire-tolerant trees such as bur and post oak grow among prairie grasses and wildflowers including little bluestem, purple coneflower, and wild indigo.